================================================================================
UNUN 16:1 — LONGWIRE ANTENNA MATCHING
================================================================================

Purpose: Impedance transformation 800Ω unbalanced → 50Ω unbalanced
Type: Voltage transformer (4:1 turns ratio unun)
Insertion Loss: 0.25–0.40 dB (significant due to extreme ratio)
Primary Use: Very high-impedance longwire antennas, specialized matching

================================================================================
CORE SPECIFICATIONS
================================================================================

HF Configuration (160M–10M):
  Core: FT-240-43 or stacked FT-240-43×2 (for low frequencies)
  Wire: #14 enameled copper
  Primary: 5 turns (antenna side, 800Ω)
  Secondary: 20 turns (coax side, 50Ω)
  Turns Ratio: 4:1 (gives 16:1 impedance transformation)
  Max Power: 350 W (high loss, thermal management important)
  Insertion Loss: 0.30–0.40 dB

Band-Specific Configuration:
  160M (1.8 MHz):   5 primary, 20 secondary (stacked cores recommended)
  80M (3.75 MHz):   5 primary, 20 secondary (single FT-240-43)
  40M (7.15 MHz):   4 primary, 16 secondary
  20M–10M:        3 primary, 12 secondary (reduced turns for impedance)

Wire Lengths:
  Primary: ~80 inches (5 turns)
  Secondary: ~150 inches (20 turns)
  Total: ~230 inches (longest winding)

================================================================================
IMPEDANCE TRANSFORMATION
================================================================================

TURNS RATIO:
  N_ratio = 20 / 5 = 4:1
  Z_out = Z_in / N² = 800 / 16 = 50Ω ✓

VOLTAGE STEP-DOWN:
  V_out = V_in × (1/4) = 0.25 × V_in

================================================================================
FREQUENCY RESPONSE
================================================================================

FT-240-43, 5:20 turns:

Frequency    Impedance Ratio    Insertion Loss
160M         16.4:1             0.40 dB
80M          15.8:1             0.35 dB
40M          15.0:1             0.28 dB
20M          14.2:1             0.22 dB
10M          13.5:1             0.18 dB

Notes:
  - Impedance ratio flat but loss significant
  - Accept 0.3–0.4 dB loss (acceptable for specialized antenna)

================================================================================
PRIMARY APPLICATIONS
================================================================================

1. VERY HIGH-IMPEDANCE LONGWIRES:
   - Wire feedpoint impedance 800Ω or higher
   - Non-resonant design, typically >300 feet length
   - 16:1 unun specializes in this extreme impedance range

2. ANTIQUE LONGWIRE ANTENNAS:
   - Historical amateur radio designs
   - Some exhibit 800–1000Ω feedpoint impedance
   - 16:1 may be close match (use with tuner for adjustment)

3. EXPERIMENTAL ANTENNA RESEARCH:
   - Testing high-impedance antenna designs
   - 16:1 allows characterization without tuner loading

================================================================================
FAILURE MODES
================================================================================

SYMPTOM: Excessive heating
ROOT CAUSE: High insertion loss (ferrite dissipation)
SOLUTION:
  - Reduce power (16:1 unun not rated for full QRO)
  - Use stacked cores (FT-240-43×2) to reduce loss
  - Consider tuner + lower-ratio unun alternative

SYMPTOM: Impedance doesn't match (high SWR)
ROOT CAUSE: Antenna impedance not exactly 800Ω
SOLUTION: Use tuner with 16:1 unun for final matching

================================================================================
TESTING PROCEDURE
================================================================================

Setup:
  Port 1: Coax 50Ω output
  Port 2: Primary antenna side (800Ω load)
  Use 800Ω resistive load for testing

Measurement: Impedance ratio with 800Ω load
  Expected: Z_out ≈ 50Ω
  S₁₁ <-20 dB (excellent match when impedance exact)

================================================================================
POWER HANDLING
================================================================================

FT-240-43 single core:
  Continuous (CW): 350 W (thermal limits)
  Peak (SSB): 500 W
  Thermal rise: ~30°C @ 350W (significant heating)

For 160M or QRO operation: Use FT-240-43×2 stacked cores

================================================================================